Copper-silicon-cadmium alloys



Patented Mar. 17, 19 36 STATES r 2,034,563 corrEa-smcoN-clmmrm ALLOYS pany, Waterbury, necticut Conn., a corporation of Con- No Drawing. Application April 26, 1935, Serial No.. 18,368

13Claims.

.This invention relates to copper-silicon alloys and has for its principal object the improvement of the tensile strength and casting properties of such alloys by the addition of cadmium.

Although the copper-silicon alloys have been known for a long time, no commercial application of copper alloys containing more than very small quantities of silicon was made until the addition of manganese was found to render them more workable (U. S. Patent No. 1,539,260-1925) Since that time the alloys have become of major industrial importance and a number of other ternary or more complex alloys containing silicon have ,been developed. While in some cases the third or additional element is added for the purpose of improving the strength or corrosion resistance of the alloys, it is probable that in most cases the principal effect is in modifying the casting characteristics, for the binary copper-silicon alloys are considered to be diflicult to cast soundly and to be very liable to contain blowholes, shrinkage cavities and drossy inclusions.

In studying the effects of a number of elements oncopper-silicon alloys we have found that the addition of cadmium greatly improves the casting qualities of copper-silicon alloys. We believe this efiect to be due partly to the effect of cadmium in dispelling and particularly in preventing the absorption of gases on account of its own high vapor pressure at the usual temperatures of casting, and partly to the comparatively fusible character of the oxides or silicates formed on the surface of the metal when exposed to air. The oxide readily collects into drops and separates from the alloy. and is not liable to become easily entrained during casting as are the films or powdery particles formed when a, pure coppersilicon is oxidized. Fortunately, the slag is not so thin that it cannot readily be skimmedirom the surface of the metal when this is at the usual pouring temperature.

The amount of cadmium that we have found necessary to have the first beneficial efiects is quite small, about 0.05 percent, but we have found that amounts even as high as 1.5 percent may be added before the malleability of the alloys 001m mences'to be seriously impaired, although beyond this point the alloys cannot be commercially hot or cold rolled. On account of the comparatively high cost of cadmium it is also preferable not to use an excess of it, and for most purposes we prefer to use about 0.5 percent.

In Table I we have by way of example given the tensile properties of some alloys representing our invention. These tests were made on strip 0.040 in. thick made by hot and cold rolling. The final reduction by cold rolling was percent following an annealing at a temperature of 700 C. The cadmium addition increases the strength and hardness of the alloy without a large effect in the ductility, but the principal mechanical properties characteristic of the alloy come from the silicon content, which should be between 0.5 and 5.0 percent, depending on the strength and duetility required and will usually be greater than the cadmium content. For many general engi neering purposes a silicon content of about 3 percent seems desirable, combined with a cadmiun. content of about 0.5 percent, but it is obvious to anyone skilled in the art that higher amounts of silicon, up to about 5 percent, would be desirable if greater strength is required, and smaller amounts of silicon if severe forming operations are to be encountered, or if for other reasons the alloy has to be unusually ductile. At the same time the cadmium content may be varied between the limits given above to maintain a suitable balance between the desired casting and fabricating qualities and cost.

have sometimes observed the presence of a thin film on the surface of the alloy after heat treat- TABLE I Tensile properties of cmer-siZicon-cadmium alloys 35 5 3 Hard (cold rolled) Soft (700 anneal) Alloy 4 Rockwell Rockwell Cd Si Yl'eldpo nt, ggg g if fi fl hardness, Yieldpoint, 53 5; gf g g hardness,

1bs./sq.1n. percent B gg lbs/sq. in. percent B m 2005 2.91 02,700 100,100 0.3 93.7 10,800 52,000 03.0 29.0 2019 0. 25 2. 35 ,450 100, 500 a 5 94. 13, 800 54, 300 02. s 30.4 33 30 a; as 33 2021 0170 2ls7 001 350 1031200 215 9513 131200 1 0513 3315 2010 0.90 2.00 05,300 105,200 0.5 94.7 13,000 54,400 07.3 30.0 33 33 20 as 3-02. 32 023 a: 23 2032 0. 79 2. 20 001 100 921400 71 3 91: 111 E00 401 000 711 5 101 s 2034 1.03 1.93 03,200 92,400 5.3 92.0 12,000 44,100 743 10.0 2029 0.30 a 0.93 00,200 07,300 3.3 74.1 0,200 30.200 43.3 -s.4 2031 0. s1 0. s9 02, 750 72, 500 4.0 79. 3 s, 000 30, 900 40. 3 -3. 5 3.2 :03 32: 2223 13-0 33 32 as 2022 0193 3100 03,450 1171700 510 9313 231000 50'400 33:2 55:9 2020 1. 03 3. 95 02,900 110, 100 2. 0 99. 3 22, 000 521300 23. s 50. 2 2024 0.73 4.35 59,700 111,300 0.5 90.7 29,000 1 59,500 21.0 00.1 2011 0.77 1.45 ,400 03,400 4.0 86.1 11,000 40,500 50.5 12.7

Tests on strip 0.040 in. thick.

Hard alloys were cold rolled 50 percent reduction following annealing for one hour at 700 0.

one hour at 700 C. after same rolling treatment.

The cadmium is added to the molten coppersilicon alloy preferably in the form of a coppercadmium alloy containing to 50 percent cadmium, since if it is added as pure cadmium the loss is very high due to the low boiling point of the element. It is an advantage to have some cadmium present in the charge to give the full benefit of its action during melting and for that reason a portion of scrap is always advisable. 'The silicon can be put in with the cold charge or it may be added (either as the element or as a copper-silicon alloy) to the molten metal, either before or after adding the cadmium.

The usual impurities may, of course, be present in the alloys. 3

In addition to their good casting qualities the alloys of copper, cadmium and silicon in the ranges given above will be found to be particularly desirable from the standpoint of fabrication. The alloys may be readily not rolled at suitable temperatures and can be extensively cold rolled. They lend themselves readily to the usual forming operations either in the hot or cold con- 4 dition. No difliculty will be encountered in either soldering or brazing the alloys. The alloys may be welded by resistance, arc or flame methods and they are also particularly suited for use as a welding rod not only for welding material of similar composition but also other materials of different types both non-ferrous and ferrous.

They may be used in the form of castings, made in sand or chill molds or in forms fabricated from wrought sheet, rod or wire. They can be extruded, hot forged or hot pressed and in addition to the hot working they may be made into wires, rods, tubes, sheets and shapes, and also may be drawn, stamped or spun into cups and other forms of drawn metal articles. Certain of the alloys with low silicon may be used for electrical purposes, although the conductivity of the alloys is not very high.

The alloys are suitable for any application wherein their strength, ductility and corrosion resistance is of advantage. They take on a good polish and are of attractive color and appearance.

During the usual processes of fabrication we slightly elevated temperatures.

Soft alloys were annealed ment, and we believe this to be definitely advantageous in increasing the resistance to corrosion under certain conditions.

The addition of cadmium materially improves the resistance of copper-silicon alloys to failure when exposed to stress in a steam atmosphere. As an example, an alloy of 3 percent silicon exposed to a certain load in a suitable steam atmosphere failed after 1 hour, while an alloy of 3 percent silicon, 1 per cent cadmium exposed under similar conditions of stress failed after 76 hours. The alloys are therefore well suited for expansion joints, flexible pipe, diaphragms, valves, and other parts exposed to steam or hot water when under stress.

The alloys have high resistance to corrosion in the atmosphere and in both hot and cold, fresh and salt water. The alloys are also suited to the construction of parts of chemical plant exposed to dilute acid or other corrosive media for whichtherefore susceptible to precipitation hardening by suitable'heat treatment. For example, we

have found that with 3 percent silicon the solubility limit is about 1.1 percent cadmium at 500 C. and 0.4 percent at400 C.; with 2 percent silicon about 1.4 and 0.6 percent cadmium; and with 1 percent silicon about 1.8 and 0.7 percent cadmium at 500 and 400 C. respectively. The increase in strength and hardness obtainable after heat treatment is not large but may be useful in some applications. Precipitation is not accompanied by any appreciable loss of ductility and the alloys are not damaged by service at Having thus set forth the nature of our invention, what we claim is:

1. An alloy composed of approximately 0.5 to 5 percent silicon, 0.05 to 1.5 percent cadmium, balance copper.

2. An alloy composed of approximately 3.0 percent silicon, 0.5 percent cadmium, balance copper.

3. An allo'y composed of approximately 2.0 percent silicon, 0.5 percent cadmium, balance copper.

4. An alloy composed of approximately 1.0 percent silicon, 0.5 percent cadmium, balance copper.

5. The alloy according to claim 1 containing from 0.01 to 0.5 percent sulphur.

6. The alloy according to claim 1 containing from 0.05 to 1 percent lead.

7. The alloy according to claim 2 containing from 0.01 to 0.5 percent sulphur.

8. The alloy according to claim 2 containing from 0.05 to 1 percent lead.

g 3 9. An alloy composed of approximately 0.5 to 5 percent silicon, 0.05 to 1.5 percent cadmium,

and balance copper; in which the silicon content exceeds the cadmium content.

10. A wrought metal article fabricated from an alloy composed of approximately 0.5 to 5 percent silicon, 0.05 to 1.5 percent cadmium, bal- &

ance copper.

11. A wrought metal article fabricated from an alloy composed of approximately 3 percent silicon, 0.5 percent cadmium, and balance copper.

12. The wrought metal article of claim 9 containing 0.01 to 0.5 percent sulphur.

13. The wrought metal article of claim 10 containing from 0.05 to 1 percent lead.

CHARLES H. DAVIS. ELMER L. MUNSON. CYRIL STANLEY SMITH. 

